We are examining the details of structural polymorphism of the major glycoprotein of human erythrocyte membrane (glycophorin). Our approach is to compare glycophorins isolated from individual donors of the M, N or MN blood types as well as immunologic and genetic variants of these blood groups. Our studies include comparison of the amino acid and carbohydrate structure of CNBr peptide A; in the coming year we plan to initiate amino acid sequence determination of the approximately 50 residue carboxy terminal CNBr peptide C. At present we are investigating the detailed structure of the complex N-asn linked oligosaccharide unit. We plan to establish whether this unit is unique within the glycoprotein and fully processed.